Have some of the ones already mentioned.
Lets see Amazon, ebay, paypal, credit union, craigslist, mobile scan,(convert receipts to pdf's) yahoo finance and email, bar code and qr scanner, compass, temp, baro, sams club, tapatalk, state game lands maps, tv off(great app like tv be gone remote) whole crapload of nfc tag apps.
Also, Torque pro, (odbII code reader) with a $12 bluetooth obd adapter from Amazon, this program will read all check engine codes, srs (airbag) codes, rpm, voltage, timing, trans temp and much more. A handheld obd code reader doesn't even come close. I don't mind paying .99c or even more for a good decent app. Some of those include conversion apps, like a engineers handbook, ruler and protractor, level, screw thread pitch sizes, electronic connector pinouts etc.etc.